166 ARMILLARIA MELLEA, 



stumps within the area must be examined for signs of rot. 

 Infected stumps break apart fairly easily and show plates 

 of deep black tissue. Further procedure will depend on the 

 extent of the area to be treated. If this is not too large the 

 infected stumps should be grubbed up, a process which is 

 far easier when the stumps are rotted than when they are 

 fresh, and all parts burned. If this involves too much 

 labour, isolation trenches should be dug round the stumps, 

 and cut to a depth at which no more rhizomorphs are 

 encountered. 



By this means the chance of infection of neighbouring 

 trees will be greatly reduced, as the rhizomorphs outside 

 the trench, being cut off from their chief base of supplies, 

 will be greatly weakened. But it may be found that some 

 living trees, which in the summer showed no sign of attack, 

 already have Armillaria growing from their roots, as in 

 figs. 69 and 70. From the base of these trees the soil should 

 be removed, and if it is found that only a few roots are 

 infected, these roots must be cut through above the points 

 of attack and grubbed up. If, however, the fungus has 

 grown into the trunk, as shown by plates of white mycelium, 

 it is better to grub up the whole trees, utilize the upper 

 part for what it is worth, and burn the remainder, otherwise 

 the trees will die shortly and become fresh bases for fungal 

 invasion. Those who pin their faith to isolation trenches 

 should remember that these are of no value unless they are 

 kept open for a long time, for the fungus is long-lived and 

 may grow on a single oak or beech stump ten years or 

 more. If, on the other hand, an infected stump is removed, 

 a trench is unnecessary, as the rhizomorphs still in the 

 ground are incapable of growth when they have been 

 severed from their base, unless they have already penetrated 

 the roots of other trees. 



The success of the measures adopted can only be tested 

 in the following autumn. If the toadstools come up again 

 next year, it is a sure sign that undiscovered bases had been 

 left, and further treatment along the same line is necessary. 

 It may' take several years to eradicate a well-established 



